A six-string guitar with a standard effective string length plays the fundamental frequency when the low E string is plucked. What is the tension in the low E string if its linear density is known? The fundamental wavelength is twice the effective string length. The wave speed is the fundamental wavelength multiplied by the fundamental frequency. Now, the string's tension is the string's linear mass density multiplied by the square of the wave speed. The expression for wave speed is substituted in the tension equation. The values of the effective string length, fundamental frequency and linear mass density are plugged into the equation to obtain the required tension at which the low E string needs to be tuned. Note that the frequency is inversely proportional to the effective string length. So, on shortening the effective string length by pressing it on any fret, one can play frequencies higher than the set frequency.